The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 599.58 crore in the futures & options segment on Wednesday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 455.92 crore and bought index options worth Rs 340.82 crore. They were net sellers of stock futures to the tune of Rs 195.88 crore and sold stock options worth Rs 1.29 crore.